The implosion that occurs upon breakage of the envelope of an evacuated cathode ray tube can be dangerous. If the faceplate is accidentally impacted, it can shatter into many fragments which may be driven into the interior of the tube envelope by atmospheric pressure. The glass fragments then rebound outwardly and can be ejected with sufficient force to cause serious injury to a person standing in front of the tube.
In the past, color television tubes have consisted of CRTs (cathode ray tubes) with convexly curved faceplates. Faceplates of this type resist external air pressure in much the same manner as an arch supports an architectural load. A band of steel under tension is applied to the periphery of the faceplate, putting the glass under compression. Effective implosion protection results in view of the fact that a blow to the faceplate results in the glass falling harmlessly, and with low velocity, into the interior of the tube
Recently, a superior color CRT was invented that employs a flat faceplate in conjunction with a tensed foil shadow mask. The implosion-protection system used successfully for tubes having curved faceplates was found to be impractical when applied to tubes having a flat faceplate.
An implosion protection system suitable for tubes having a flat faceplate is fully described and claimed in U.S. Pat. Nos. 4,739,412 and 4,841,372, of common ownership herewith. A resin-bonding system is disclosed in which a implosion-protection panel is bonded to the faceplate of a cathode ray tube, and the resin is cured by ultraviolet radiation. The resin-bonding system is designed for differential adhesion such that the faceplate separates more easily from the resin than does the implosion protection panel. The two patents set forth in detail the composition of the resins and release agents, and describe a means and process on which the present invention is based.
In U.S. Pat. No. 3,879,627 to Robinder, a display tube having a neutral density filter is disclosed. A sheet of glass is placed in spaced, overlying relationship with a faceplate. A securing tape is mounted around the circumference of the two members and holds the members in a predetermined spaced relation. Heat of about 60 degree C. is applied and the space between the faceplate and panel is filled with resin, after which the final assembly is cooled and the resin is allowed to cool and set.